This invention relates generally to a coating apparatus, and more particularly to such an apparatus for coating a liquid on to a surface of a rotating workpiece using at least one stationary wick applicator.
Ferrofluids, viscous magnetic damping materials, are used in loudspeaker applications in the gap area between voice coil and polepiece of a driver assembly. Contamination upon contact with primer or adhesive in this area can cause coagulation, separation, thinning or thickening of the ferrofluid which will cause speaker failure. During the loudspeaker assembly operation, the speaker magnets are normally bonded into place by an adhesive which must avoid any loosening or dislodgement of the magnet during handling or in the presence of heat. Adhesive of the uncured variety may be used, together with a selected primer or activator, but are found incompatible with ferrofluids. Extreme care must thus be exercised in coating the primer on the magnetic disc to avoid any contact with the ferrofluids in the region of the central opening of the disc, which may cause coagulation or separation of the ferrofluid.
Speaker magnets are typically assembled by painting, spraying or dipping the magnets with the selected primer. Because of its low viscosity relative to the adhesive which is applied to a mating part, any operator error of over or under priming will affect speaker quality and even failure. These techniques are imprecise since they are carried out by hand and leave the amount of primer applied up to the discretion of the operator. They may also have dermititus problems during skin contact with the primer, and may result in disc chipping during handling of the ferrite magnet made of a low density ceramic.